1. Field
Disclosed herein is an apparatus and a method of continuously measuring blood pressure of an examinee using a tonometric method.
2. Description of the Related Art
Various types of blood pressure measuring apparatuses have been developed in response to increasing public concerns about health. Examples of blood pressure measuring methods include a Korotkoff sound method, an oscillometric blood pressure measuring method, a tonometric blood pressure measuring method, and the like. The Korotkoff sound method is a typical pressure measuring method, which measures the systolic pressure at which the pulse sound of a living being is first heard and the diastolic pressure at which the pulse sound is barely audible during a decompression process. For the Korotkoff sound method a pressure is applied to a part of a body where arterial blood flows and the blood flow is blocked and then the applied pressure is reduced. As the pressure is reduced, a first pressure is measured when a sound of the pulse of a living being is heard first as a systolic pressure and a last pressure is measured at which the sound of the pulse a living being disappears as a diastolic pressure.
The oscillometric method and the tonometric method are used for digital blood pressure measuring apparatuses. The oscillometric method detects a sphygmus wave, which occurs in a decompression process after sufficiently compressing a body part through which arterial blood flows so as to block arterial blood flow in a manner that is similar to the Korotkoff sounds method, or in a compression process in which the body part is compressed at a predetermined compression speed. A pressure at which the amplitude of the sphygmus wave is at a specific level may be measured as a systolic pressure or as a diastolic pressure. Alternatively, a pressure at which the amplitude of the sphygmus wave changes suddenly may be measured as a systolic pressure or as a diastolic pressure.
During the decompressing process at a predetermined compression speed after compressing the body part, a systolic pressure is measured prior to a point of time at which the amplitude of the sphygmus wave is at a maximum, and a diastolic pressure is measured after a point of time at which the amplitude of the sphygmus wave is at the maximum. On the other hand, during the compression speed, a systolic pressure is measured after the point of time at which the amplitude of the sphygmus wave is at the maximum, and a diastolic pressure is measured prior to the point of time at which the amplitude of the sphygmus wave is at the maximum.
The tomometric method includes applying a certain pressure to a body part so that the arterial blood flow is not completely blocked and continuously measuring the blood pressure using the amplitude and form of a sphygmus wave that is generated by compressing the body part. Since the tonometric method requires continuously applying pressure for a long time, it may be burdensome to the examinee. Meanwhile, when the measured blood pressure abruptly changes during the measuring of the blood pressure by the tonometric method, it should be determined whether this change is caused by the actual change in the blood pressure of the examinee or by the inaccuracy of applying pressure the body part.